What data is being used?

The a11y-Score is calculated using data that is freely available via OpenStreetMap (OSM). OSM is a collaborative world map created and maintained jointly by volunteers and professionals. The community isn't just made up of individual enthusiasts—government agencies are often involved as well.

OpenStreetMap and Tags

The basis for the accessibility criteria we evaluate is what are known as tags. A tag is essentially a label attached to an object on the map. It provides information that goes beyond mere geography (the location). Without such tags, all you would know about a location on the map is where it is, but not what it is — a café, a train station, a doctor’s office or e.g. accessible without steps.

A tag always consists of two parts: a key and a value. It’s usually written like this: key=value. For example, “wheelchair=yes” means that a geographic object is wheelchair-accessible.

Tags enable computers to “understand” and filter the map. For example, to calculate how accessible a train platform is, the a11y-Score algorithm looks for specific tags such as tactile_paving=yes (meaning there is a tactile paving system) or wheelchair=yes (meaning the platform is wheelchair-accessible).